BACKGROUND
It is known that houseplants support complex biological and bacterial processes within the plant and also within the growth medium surrounding the plant roots, within which the plant is embedded, all of which tend to biodegrade various airborne pollutants, especially airborne hydrocarbons. This is summarized in Applicant's aforesaid patents.
The fact that low-light requiring houseplants culture microorganisms on and around their roots capable of destroying indoor air polluting chemicals have been demonstrated by B. C. Wolverton and John D. Wolverton (1993), "Plants and Soil Microorganisms: Removal of Formaldehyde, Xylene and Ammonia From The Indoor Environment," Journal of the Mississippi Academy of Science 38 (2) 11-15. The fact that certain houseplants can suppress levels of airborne microbes and add water vapor to rooms in which they are maintained has also been demonstrated by B. C. Wolverton and John D. Wolverton (1993) "Interior Plants: Their Influence On Airborne Microbes and Relative Humidity Levels Inside Energy-Efficient Buildings," Research Report No. WES/100/05-93/011; pp. 1-19; Plants for Clean Air Council, 10210 Bald Hill Road, Mitchellville, Md. 20721.
Prior art purification devices have been shown in U.S. Pat. No. 4,975,251 to Saceman in which a mechanical fan directs air into overlying soil in which certain plants grow to purify the air.
U.S. Pat. No. 4,786,812 to Humphries shows use of ultraviolet lamps to kill germs in moving air. The use of ultraviolet light as a bactericide has been widely known.
U.S. Pat. No. 4,845,602 to Lohecki shows a combined lamp and container apparatus.
A significant problem in regards to the use of plants and plant soil for purification of airborne contaminants is that the passage of air past the plant and especially through the plant's soil, tends to rapidly remove water, either by aspiration from the leaves of the plant or by evaporation from the soil particles. There is an optimum humidity for the soil in which a plant is embedded for best use as an air purifying medium; too much humidity blocks air flow and air purification, too little humidity results in the death of the plant.
There is also a known optimum humidity for human comfort. However, it has been discovered that maintaining a relatively high humidity from the point of comfort also significantly increases the incidence of airborne spores and bacterial contamination, which also propagate in higher humidity environments. In addition, various molds, fungi and other micro-organisms flourish under the humidity conditions that humans generally find most comfortable.